Reading the other threads it seems I have to make some change to a CoutlAddon .ini which is supposed to be in my ProgramData\User\Roaming\Virtuali folder but that folder has no .ini file there!
That file is not supposed to be already there, it might be, but only if you changed some options, like the extended logging, but everything is default, it's entirely normal the file wouldn't be there. Just create it or, enable logging in the GSX Settings, which will also create the file.
To that file, you'll have to add this line. I'm making an EXAMPLE to consider AFCADs all files up to 4MB in size.
airportCacheMaxBGLSizeBytes = 4000000000
I also tried to follow threads where Umberto referred to other threads to solve this but ran into a brick wall when it told me I didn't have permissions to look in there??
The topic you are probably referring to is here:
http://www.fsdreamteam.com/forum/index.php/topic,13489.msg100092.html#msg100092 I have got GSX loaded I can't use it at any airport because the error message "could not find AFCAD at this position"
If with "any airport", you really mean EVERY airport, then I'm afraid there must be another issue here, because by default, even without that line, GSX will consider as *possible* AFCADs all .BGL files up to 1.2MB and, since 99% of the AFCAD ( including all default scenery ) are far smaller than that, setting the maxim size should only be required if you have some specific add-ons that have larger AFCAD, which are not very common.